Synthesis and polyelectrolyte behavior of poly(methacrylic acid) star polymers

Poly(tert‐butyl methacrylate) [P(tBMA)] star polymers were synthesized by copolymerization of p(tBMA) macroinitiator with ethylene glycol dimethacrylate via atom transfer radical polymerization method. P(tBMA) stars had a narrow molecular weight distribution (M_w/M_n = 1.06–1.15). The ratio of radius of gyration to hydrodynamic radius R_G/R_H, which indicates inner segment density, was in the range 1.16–1.22 in tetrahydrofuran (THF) (arm number f = 25–142). These stars behaved not as hard spheres but as soft spheres in THF. Poly(methacrylic acid) stars were obtained by the hydrolysis of P(tBMA) arms. We investigated the conformation of star polyelectrolyte as a function of pH and ionic strength by means of dynamic light scattering (DLS). The hydrodynamic diameter increased gradually from 18.8 to 48.3 nm as a function of the solution pH. In addition, we compared experimental results with theoretical models for star polyelectrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007